Optical device structure using GaN substrates and growth structure for laser applications

ABSTRACT

An optical device having a structured active region configured for one or more selected wavelengths of light emissions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.12/762,278, filed Apr. 16, 2010; which claims priority to U.S.Application No. 61/170,550, filed Apr. 17, 2009; U.S. Application No.61/170,553, filed Apr. 17, 2009; U.S. Application No. 61/177,217, filedMay 11, 2009; U.S. application Ser. No. 12/534,829, filed Aug. 3, 2009;which claims priority to U.S. Application No. 61/243,502, filed Sep. 17,2009; and U.S. application Ser. No. 12/759,273, filed Apr. 13, 2010,each of which is commonly assigned and hereby incorporated by reference.

BACKGROUND OF THE INVENTION

This invention is directed to optical devices and related methods. Moreparticularly, the invention provides a method of manufacture and adevice for emitting electromagnetic radiation using semipolar ornon-polar gallium containing substrates such as GaN, MN, InN, InGaN,AlGaN, and AlInGaN, and others. Merely by way of example, the inventioncan be applied to optical devices, lasers, light emitting diodes, solarcells, photoelectrochemical water splitting and hydrogen generation,photodetectors, integrated circuits, and transistors, among otherdevices.

In 1960, the laser was first demonstrated by Theodore H. Maiman atHughes Research Laboratories in Malibu. This laser utilized asolid-state flash lamp-pumped synthetic ruby crystal to produce redlaser light at 694 nm. By 1964, blue and green laser output wasdemonstrated by William Bridges at Hughes Aircraft utilizing a gas Argonion laser. The Ar-ion laser utilized a noble gas as the active mediumand produced laser light output in the UV, blue, and green wavelengthsincluding 351 nm, 454.6 nm, 457.9 nm, 465.8 nm, 476.5 nm, 488.0 nm,496.5 nm, 501.7 nm, 514.5 nm, and 528.7 nm. The Ar-ion laser had thebenefit of producing highly directional and focusable light with anarrow spectral output, but the wall plug efficiency was less than 0.1%.The size, weight, and cost of the laser was undesirable as well.

As laser technology evolved, more efficient lamp pumped solid statelaser designs were developed for the red and infrared wavelengths, butthese technologies remained a challenge for blue and green lasers. As aresult, lamp pumped solid state lasers were developed in the infrared,and the output wavelength was converted to the visible using specialtycrystals with nonlinear optical properties. A green lamp pumped solidstate laser had 3 stages: electricity powers lamp, lamp excites gaincrystal which lases at 1064 nm, 1064 nm goes into frequency conversioncrystal which converts to visible 532 nm. The resulting green and bluelasers were called “lamped pumped solid state lasers with secondharmonic generation” (LPSS with SHG). These had wall plug efficiency of˜1%, and were more efficient than Ar-ion gas lasers, but were still tooinefficient, large, expensive, and fragile for broad deployment outsideof specialty scientific and medical applications. Additionally, the gaincrystal used in the solid state lasers typically had energy storageproperties which made the lasers difficult to modulate at high speeds,limiting broader deployment.

To improve the efficiency of these visible lasers, high power diode (orsemiconductor) lasers were utilized. These “diode pumped solid statelasers with SHG” (DPSS with SHG) had 3 stages: electricity powers 808 nmdiode laser, 808 nm excites gain crystal which lases at 1064 nm, 1064 nmgoes into frequency conversion crystal which converts to visible 532 nm.The DPSS laser technology extended the life and improved the wall plugefficiency of the LPSS lasers to 5-10%. This sparked furthercommercialization into specialty industrial, medical, and scientificapplications. The change to diode pumping, however, increased the systemcost and required precise temperature controls, leaving the laser withsubstantial size and power consumption. The result did not address theenergy storage properties which made the lasers difficult to modulate athigh speeds.

As high power laser diodes evolved and new specialty SHG crystals weredeveloped, it became possible to directly convert the output of theinfrared diode laser to produce blue and green laser light output. These“directly doubled diode lasers” or SHG diode lasers had 2 stages:electricity powers 1064 nm semiconductor laser, 1064 nm goes intofrequency conversion crystal which converts to visible 532 nm greenlight. These lasers designs are intended to provide improved efficiency,cost and size compared to DPSS-SHG lasers, but the specialty diodes andcrystals required make this challenging today. Additionally, while thediode-SHG lasers have the benefit of being directly modulated, theysuffer from sensitivity to temperature which limits their application.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a method and device for emittingelectromagnetic radiation using semipolar gallium or non-polarcontaining substrates such as GaN, MN, InN, InGaN, AlGaN, and AlInGaN,and others. The invention can be applied to optical devices, lasers,light emitting diodes, solar cells, photoelectrochemical water splittingand hydrogen generation, photodetectors, integrated circuits, andtransistors, among other devices.

In a specific embodiment, the present invention provides an opticaldevice configured to emit electromagnetic radiation. The device includesa gallium nitride substrate member having a nonpolar crystalline surfaceregion. The device includes an n-type GaN cladding layer overlying thesurface region. The n-type GaN cladding layer has a thickness from 100nm to 3000 nm and a Si doping level of 1E17 to 5E19 cm-3. The devicealso has an n-side SCH layer overlying the n-type GaN cladding layer.The n-side SCH layer is comprised of InGaN and having a molar fractionof indium of between 3% and 7% and a thickness from 20 to 150 nm. Thedevice has a multiple quantum well active region overlying the n-sideSCH layer, the multiple quantum well active region comprising aplurality of 3.5-7.5 nm InGaN quantum wells separated by 1.5-7.5 nm GaNor InGaN barriers. The device has a p-type cladding layer overlying themultiple quantum well active region. The p-type cladding layer has athickness from 400 nm to 1000 nm with Mg doping level of 5E17 cm-3 to5E19 cm-3. The device has a p++-type contact layer overlying the p-typecladding layer. The p++-type contact layer has a thickness from 10 nm to50 nm with Mg doping level of 5E19 cm-3 to 1E21 cm-3.

In an alternative embodiment, the present invention provides an opticaldevice configured on a semipolar oriented substrate. The device has agallium nitride substrate member having a semipolar crystalline surfaceregion. The device has an n-GaN cladding layer overlying the surfaceregion. The n-GaN cladding layer has a thickness from 100 nm to 3000 nmand a Si doping level of 1E17 to 5E19 cm-3. The device has an n-side SCHlayer overlying the n-GaN cladding layer. The n-side SCH layer iscomprised of InGaN and having a molar fraction of indium of between 3%and 8% and a thickness from 20 to 150 nm. The device has a multiplequantum well active region overlying the n-side SCH layer. The multiplequantum well active region comprises a plurality of 2.5-6.5 nm InGaNquantum wells separated by 2.5-8.0 nm GaN or InGaN barriers and a p-typecladding layer overlying the electron blocking layer. The p-typecladding layer has a thickness from 400 nm to 1000 nm with Mg dopinglevel of 5E17 cm-3 to 5E19 cm-3. The device has a p++-type contact layeroverlying the p-type cladding layer. The p++-type contact layer has athickness from 10 nm to 50 nm with Mg doping level of 5E19 cm-3 to 1E21cm-3.

The present invention enables a cost-effective optical device for laserapplications. In a specific embodiment, the present optical device canbe manufactured in a relatively simple and cost effective manner. Thepresent laser device uses a semipolar or non-polar gallium nitridematerial to provide a green laser device capable of emitting wavelengthsranging from about 470 nm to greater than about 530 nm.

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the latter portions of thespecification and attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a laser device fabricated on asemipolar substrate.

FIG. 1B is a perspective view of a laser device fabricated on anon-polar substrate.

FIG. 2 is a cross-sectional view of a laser device fabricated on anon-polar substrate.

FIG. 3 is a diagram illustrating an epitaxial laser structure.

FIGS. 4 through 6 are diagrams illustrating a laser device.

FIGS. 7 through 8 are diagrams illustrating a laser device.

FIGS. 9 through 10 are diagrams illustrating a laser device.

FIGS. 11 through 13 are diagrams illustrating a laser device.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a method and device for emittingelectromagnetic radiation using semipolar or non-polar galliumcontaining substrates such as GaN, MN, InN, InGaN, AlGaN, and AlInGaN,and others. The invention can be applied to optical devices, lasers,light emitting diodes, solar cells, photoelectrochemical water splittingand hydrogen generation, photodetectors, integrated circuits, andtransistors, among other devices. The present laser device can beemployed in either a semipolar or non-polar gallium containingsubstrate, as described below.

In a specific embodiment, the invention provides an optical device. Theoptical device includes a gallium nitride substrate member having anonpolar or semipolar crystalline surface region. The device also has ann-GaN cladding layer overlying the surface region. Preferably, the n-GaNcladding layer has a thickness from 100 nm to 3000 nm and a Si dopinglevel of 5E17 to 3E18 cm-3. The device has an n-side SCH layer overlyingthe n-GaN cladding layer. Preferably, the n-side SCH layer is comprisedof InGaN and has a molar fraction of indium of between 3% and 7% and athickness from 40 to 60 nm. The device also has a multiple quantum wellactive region overlying the n-side SCH layer. The multiple quantum wellactive region is comprising seven 3.5-4.5 nm InGaN quantum wellsseparated by eight 9.5-10.5 nm GaN barriers. In a specific embodiment,the device has a p-side SCH layer overlying the multiple quantum wellactive region. The p-side SCH layer is comprised of InGaN with molar afraction of indium of between 2% and 5% and a thickness from 15 nm to 25nm according to a preferred embodiment. The device also has an electronblocking layer overlying the p-side SCH layer. Preferably, the electronblocking layer is comprised of AlGaN with molar fraction of aluminum ofbetween 15% and 22% and a thickness from 10 nm to 15 nm and doped withMg. The optical device has a p-GaN cladding layer overlying the electronblocking layer. Preferably, the p-GaN cladding layer has a thicknessfrom 400 nm to 1000 nm with Mg doping level of 5E17 cm-3 to 1E19 cm-3.In a specific embodiment, the device has a p++-GaN contact layeroverlying the p-GaN cladding layer. Preferably, the p++-GaN contactlayer having a thickness from 20 nm to 40 nm with Mg doping level of1E20 cm-3 to 1E21 cm-3.

FIG. 1A is a simplified perspective view of a laser device 100fabricated on a semipolar substrate according to an embodiment of thepresent invention. This diagram is merely an example, which should notunduly limit the scope of the claims herein. One of ordinary skill inthe art would recognize other variations, modifications, andalternatives. As shown, the optical device includes a gallium nitridesubstrate member 101 having a semipolar or non-polar crystalline surfaceregion. The gallium nitride substrate member is a bulk GaN substratecharacterized by having a semipolar or non-polar crystalline surfaceregion, but can be others. In a specific embodiment, the bulk nitrideGaN substrate comprises nitrogen and has a surface dislocation densitybelow 10⁵ cm⁻². The nitride crystal or wafer may compriseAl_(x)In_(y)Ga_(1-x-y)N, where 0≦x, y, x+y≦1. The nitride crystalpreferably comprises GaN. Typically the GaN substrate has threadingdislocations, at a concentration between about 10⁵ cm⁻² and about 10⁸cm⁻², in a direction that is substantially orthogonal or oblique withrespect to the surface. As a consequence of the orthogonal or obliqueorientation of the dislocations, the surface dislocation density isbelow about 10⁵ cm⁻². In a specific embodiment, the device can befabricated on a slightly off-cut semipolar substrate as described inU.S. Provisional No. 61/164,409 filed Mar. 28, 2009, commonly assigned,and hereby incorporated by reference herein.

On semipolar GaN, the device has a laser stripe region formed overlyinga portion of the semi polar crystalline orientation surface region. In aspecific semipolar GaN embodiment, the laser stripe region ischaracterized by a cavity orientation is substantially parallel to them-direction. In a specific embodiment, the laser strip region has afirst end 107 and a second end 109.

On nonpolar GaN, the device has a laser stripe region formed overlying aportion of the semi or non-polar crystalline orientation surface region,as illustrated by FIG. 1B, for example. In a specific embodiment, thelaser stripe region is characterized by a cavity orientation issubstantially parallel to the c-direction. The laser strip region has afirst end and a second end. The non-polar crystalline orientation isconfigured on an m-plane, which leads to polarization ratios parallel tothe a-direction. The more embodiments, the m-plane is the (10-10)family. Of course, there cavity orientation can also be substantiallyparallel to the a-direction as well. In the specific nonpolar GaNembodiment having the cavity orientation substantially parallel to thec-direction is further described in “Laser Device and Method UsingSlightly Miscut Non-Polar GaN Substrates,” in the names of Raring, JamesW. and Pfister, Nick listed as U.S. Provisional Ser. No. 61/168,926filed Apr. 13, 2009, commonly assigned, and hereby incorporated byreference for all purposes.

In a preferred semipolar embodiment, the device has a first cleavedm-face facet provided on the first end of the laser stripe region and asecond cleaved m-face facet provided on the second end of the laserstripe region. In one or more embodiments, the first cleaved m-facet issubstantially parallel with the second cleaved m-facet. In a specificembodiment, the semipolar substrate is configured on (11-22) series ofplanes, which enables the formation of m-facets for laser cavitiesoriented in the m-direction. Mirror surfaces are formed on each of thecleaved surfaces. The first cleaved m-facet comprises a first mirrorsurface. In a preferred embodiment, the first mirror surface is providedby a scribing and breaking process. The scribing process can use anysuitable techniques, such as a diamond scribe or laser scribe orcombinations. In a specific embodiment, the first mirror surfacecomprises a reflective coating. The reflective coating is selected fromsilicon dioxide, hafnia, and titaniatantalum pentoxidezirconia,including combinations, and the like. Depending upon the embodiment, thefirst mirror surface can also comprise an anti-reflective coating.

In a preferred nonpolar embodiment, the device has a first cleavedc-face facet provided on the first end of the laser stripe region and asecond cleaved c-face facet provided on the second end of the laserstripe region. In one or more embodiments, the first cleaved c-facet issubstantially parallel with the second cleaved c-facet. In a specificembodiment, the nonpolar substrate is configured on (10-10) series ofplanes, which enables the formation of c-facets for laser cavitiesoriented in the c-direction. Mirror surfaces are formed on each of thecleaved surfaces. The first cleaved c-facet comprises a first mirrorsurface. In a preferred embodiment, the first mirror surface is providedby a scribing and breaking process. The scribing process can use anysuitable techniques, such as a diamond scribe or laser scribe orcombinations. In a specific embodiment, the first mirror surfacecomprises a reflective coating. The reflective coating is selected fromsilicon dioxide, hafnia, and titaniatantalum pentoxidezirconia,including combinations, and the like. Depending upon the embodiment, thefirst mirror surface can also comprise an anti-reflective coating.

Also in a preferred semipolar embodiment, the second cleaved m-facetcomprises a second mirror surface. The second mirror surface is providedby a scribing and breaking process according to a specific embodiment.Preferably, the scribing is diamond scribed or laser scribed or thelike. In a specific embodiment, the second mirror surface comprises areflective coating, such as silicon dioxide, hafnia, and titaniatantalumpentoxidezirconia, combinations, and the like. In a specific embodiment,the second mirror surface comprises an anti-reflective coating.

Also in a preferred nonpolar embodiment, the second cleaved c-facetcomprises a second mirror surface. The second mirror surface is providedby a scribing and breaking process according to a specific embodiment.Preferably, the scribing is diamond scribed or laser scribed or thelike. In a specific embodiment, the second mirror surface comprises areflective coating, such as silicon dioxide, hafnia, and titaniatantalumpentoxidezirconia, combinations, and the like. In a specific embodiment,the second mirror surface comprises an anti-reflective coating.

The laser stripe has a length and width. The length ranges from about 50microns to about 3000 microns. The strip also has a width ranging fromabout 0.5 microns to about 50 microns, but can be other dimensions.Preferably, the width is substantially constant in dimension, althoughthere may be slight variations. The width and length are often formedusing a masking and etching process, which are commonly used in the art.

In a semipolar embodiment, the device is also characterized by aspontaneously emitted light that is polarized in substantially parallelto the projection of the c-direction. That is, the device performs as alaser or the like. In a preferred embodiment, the spontaneously emittedlight is characterized by a polarization ratio of greater than about 0.2and less than about 1 parallel to the projection of the c-direction. Ina preferred embodiment, the spontaneously emitted light characterized bya wavelength ranging from about 500 to about 580 nanometers to yield agreen laser and others and the spontaneously emitted light is highlypolarized and is characterized by a polarization ratio parallel to theprojection of the c-direction of greater than 0.4.

In a nonpolar embodiment, the device is also characterized by aspontaneously emitted light that is polarized parallel to thea-direction. That is, the device performs as a laser or the like. In apreferred embodiment, the spontaneously emitted light is characterizedby a polarization ratio of greater than about 0.1 and less than about 1parallel to the projection of the c-direction. In a preferredembodiment, the spontaneously emitted light characterized by awavelength ranging from about 475 to about 530 nanometers to yield ablue-green or green laser and others and the spontaneously emitted lightis highly polarized and is characterized by a polarization ratioparallel to the a-direction of greater than 0.5.

FIG. 2 is a detailed cross-sectional view of a laser device 200fabricated on a non-polar substrate according to an embodiment of thepresent invention. This diagram is merely an example, which should notunduly limit the scope of the claims herein. One of ordinary skill inthe art would recognize other variations, modifications, andalternatives. As shown, the laser device includes gallium nitridesubstrate 203, which has an underlying n-type metal back contact region201. In a specific embodiment, the metal back contact region is made ofa suitable material such as those noted below and others.

The device also has an overlying n-type gallium nitride layer 205, anactive region 207, and an overlying p-type gallium nitride layerstructured as a laser stripe region 209. In a specific embodiment, eachof these regions is formed using at least an epitaxial depositiontechnique of metal organic chemical vapor deposition (MOCVD), molecularbeam epitaxy (MBE), or other epitaxial growth techniques suitable forGaN growth. In a specific embodiment, the epitaxial layer is a highquality epitaxial layer overlying the n-type gallium nitride layer. Insome embodiments the high quality layer is doped, for example, with Sior O to form n-type material, with a dopant concentration between about10¹⁶ cm⁻³ and 10²⁰ cm⁻³.

An n-type Al_(u)In_(v)Ga_(1-u-v)N layer, where 0≦u, v, u+v≦1, isdeposited on the substrate. In a specific embodiment, the carrierconcentration may lie in the range between about 10¹⁶ cm⁻³ and 10²⁰cm⁻³. The deposition may be performed using metalorganic chemical vapordeposition (MOCVD) or molecular beam epitaxy (MBE).

As an example, the bulk GaN substrate is placed on a susceptor in anMOCVD reactor. After closing, evacuating, and back-filling the reactor(or using a load lock configuration) to atmospheric pressure, thesusceptor is heated to a temperature between about 1000 and about 1200degrees Celsius in the presence of a nitrogen-containing gas. In onespecific embodiment, the susceptor is heated to approximately 1100degrees Celsius under flowing ammonia. A flow of a gallium-containingmetalorganic precursor, such as trimethylgallium (TMG) ortriethylgallium (TEG) is initiated, in a carrier gas, at a total ratebetween approximately 1 and 50 standard cubic centimeters per minute(sccm). The carrier gas may comprise hydrogen, helium, nitrogen, orargon. The ratio of the flow rate of the group V precursor (ammonia) tothat of the group III precursor (trimethylgallium, triethylgallium,trimethylindium, trimethylaluminum) during growth is between about 2000and about 12000. A flow of disilane in a carrier gas, with a total flowrate of between about 0.1 and 10 sccm, is initiated.

The laser stripe region is made of the p-type gallium nitride layer 209.In a specific embodiment, the laser stripe is preferably provided by dryetching, but wet etching can be used. As an example, the dry etchingprocess is an inductively coupled process using chlorine bearing speciesor a reactive ion etching process using similar chemistries. Thechlorine bearing species are commonly derived from chlorine gas or thelike. The device also has an overlying dielectric region, which exposes213 contact region. In a specific embodiment, the dielectric region isan oxide such as silicon dioxide or silicon nitride, but can be others.The contact region is coupled to an overlying metal layer 215. Theoverlying metal layer is a multilayered structure containing gold andplatinum (Pt/Au), but can be others.

The laser device has active region 207 which can include one to twentyquantum well regions. Following deposition of the n-typeAl_(u)In_(v)Ga_(1-u-v)N layer for a predetermined period of time, so asto achieve a predetermined thickness, an active layer is deposited. Theactive layer may comprise a single quantum well or a multiple quantumwell, with 1-20 quantum wells. The quantum wells may comprise InGaNwells and GaN barrier layers. In other embodiments, the well layers andbarrier layers comprise Al_(w)In_(x)Ga_(1-w-x)N andAl_(y)In_(z)Ga_(1-y-z)N, respectively, where 0≦w, x, y, z, w+x, y+z≦1,where w<u, y and/or x>v, z so that the bandgap of the well layer(s) isless than that of the barrier layer(s) and the n-type layer. The welllayers and barrier layers may each have a thickness between about 1 nmand about 40 nm. In another embodiment, the active layer comprises adouble heterostructure, with an InGaN or Al_(w)In_(x)Ga_(1-w-x)N layerabout 10 nm to 100 nm thick surrounded by GaN or Al_(y)In_(z)Ga_(1-y-z)Nlayers, where w<u, y and/or x>v, z. The composition and structure of theactive layer are chosen to provide light emission at a preselectedwavelength. The active layer may be left undoped (or unintentionallydoped) or may be doped n-type or p-type.

The active region can also include an electron blocking region, and aseparate confinement heterostructure. In some embodiments, an electronblocking layer is deposited. The electron-blocking layer may compriseAl_(s)In_(t)Ga_(1-s-t)N, where 0≦s, t, s+t≦1, with a higher bandgap thanthe active layer, and may be doped p-type. In one embodiment, theelectron blocking layer comprises AlGaN. In another embodiment, theelectron blocking layer comprises an AlGaN/GaN super-lattice structure,with alternating layers of AlGaN and GaN, each with a thickness betweenabout 0.2 nm and about 5 nm.

As noted, the p-type gallium nitride structure, which can be a p-typedoped Al_(q)In_(r)Ga_(1-q-r)N, where 0≦q, r, q+r≦1, layer is depositedabove the active layer. The p-type layer may be doped with Mg, to alevel between about 10¹⁶ cm⁻³ and 10²² cm⁻³, and may have a thicknessbetween about 5 nm and about 1000 nm. The outermost 1-50 nm of thep-type layer may be doped more heavily than the rest of the layer, so asto enable an improved electrical contact. In a specific embodiment, thelaser stripe is provided by an etching process selected from dry etchingor wet etching. In a preferred embodiment, the etching process is dry,but can be others. The device also has an overlying dielectric region,which exposes 213 contact region. In a specific embodiment, thedielectric region is an oxide such as silicon dioxide.

In a specific embodiment, the metal contact is made of suitablematerial. The reflective electrical contact may comprise at least one ofsilver, gold, aluminum, nickel, platinum, rhodium, palladium, chromium,or the like. The electrical contact may be deposited by thermalevaporation, electron beam evaporation, electroplating, sputtering, oranother suitable technique. In a preferred embodiment, the electricalcontact serves as a p-type electrode for the optical device. In anotherembodiment, the electrical contact serves as an n-type electrode for theoptical device.

FIG. 3 is a simplified diagram illustrating a laser structure accordingto a preferred embodiment of the present invention. This diagram ismerely an example, which should not unduly limit the scope of the claimsherein. One of ordinary skill in the art would recognize othervariations, modifications, and alternatives. In a specific embodiment,the device includes a starting material such as a bulk nonpolar orsemipolar GaN substrate, but can be others. In a specific embodiment,the device is configured to achieve emission wavelength ranges of 390 nmto 530 nm.

In a preferred embodiment, the growth structure is configured usingbetween 3 and 5 or 5 and 7 quantum wells positioned between n-type GaNand p-type GaN cladding layers. In a specific embodiment, the n-type GaNcladding layer ranges in thickness from 500 nm to 2000 nm and has ann-type dopant such as Si with a doping level of between 1E18 cm-3 and3E18 cm-3. In a specific embodiment, the p-type GaN cladding layerranges in thickness from 500 nm to 1000 nm and has a p-type dopant suchas Mg with a doping level of between 1E17 cm-3 and 5E19 cm-3. In aspecific embodiment, the Mg doping level is graded such that theconcentration would be lower in the region closer to the quantum wells.

In a preferred embodiment, the quantum wells have a thickness of between3 nm and 5.5 nm or 5.5 nm and 8 nm, but can be others. In a specificembodiment, the quantum wells would be separated by barrier layers withthicknesses between 4 nm and 8 nm or 8 nm and 12 nm. The quantum wellsand the barriers together comprise a multiple quantum well (MQW) region.

Also in a preferred embodiment, the device has barrier layers formedfrom GaN or InGaN. In a specific embodiment using InGaN, the indiumcontents range from 1% to 5% (mole percent), but can be others. Ofcourse, there can be other variations, modifications, and alternatives.Also, it should be noted that % of indium or aluminum is in a molarfraction, not weight percent.

An InGaN separate confinement hetereostructure layer (SCH) could bepositioned between the n-type GaN cladding and the MQW region accordingto one or more embodiments. Typically, such separate confinement layeris commonly called the n-side SCH. The n-side SCH layer ranges inthickness from 10 nm to 50 nm or 50 nm to 100 nm and ranges in indiumcomposition from 1% to 7% (mole percent), but can be others. In aspecific embodiment, the n-side SCH layer may or may not be doped withan n-type dopant such as Si.

In yet another preferred embodiment, an InGaN separate confinementhetereostructure layer (SCH) is positioned between the p-type GaNcladding and the MQW region, which is called the p-side SCH. In aspecific embodiment, the p-side SCH layer ranges in thickness from 10 nmto 50 nm or 50 nm to 100 nm and ranges in indium composition from 1% to7% (mole percent), but can be others. The p-side SCH layer may or maynot be doped with a p-type dopant such as Mg. In another embodiment, thestructure would contain both an n-side SCH and a p-side SCH.

In another embodiment, an AlGaN electron blocking layer, with analuminum content of between 14% and 22% (mole percent), is positionedbetween the MQW and the p-type GaN cladding layer either within thep-side SCH or between the p-side SCH and the p-type GaN cladding. TheAlGaN electron blocking layer ranges in thickness from 10 nm to 20 nmand is doped with a p-type dopant such as Mg from 1E18 cm-3 and 1E20cm-3 according to a specific embodiment. Preferably, a p-contact layerpositioned on top of and is formed overlying the p-type cladding layer.The p-contact layer would be comprised of GaN doped with a p-dopant suchas Mg at a level ranging from 1E20 cm-3 to 1E22 cm-3.

Embodiment A

In this embodiment, the laser device is capable of emitting 474 nm andalso 485 nm or 470 nm to 490 nm wavelength light, among others. Thedevice is provided with the following elements, as also referenced inFIGS. 4 through 6.

n-GaN cladding layer with a thickness from 100 nm to 3000 nm with Sidoping level of 5E17 to 3E18 cm-3

n-side SCH layer comprised of InGaN with molar fraction of indium ofbetween 3% and 5% and thickness from 45 to 65 nm.

Multiple quantum well active region layers comprised of five 4.5-5.5 nmInGaN quantum wells separated by six 4.5-5.5 nm GaN barriers

p-side SCH layer comprised of InGaN with molar fraction of indium ofbetween 3% and 5% and thickness from 45 nm to 65 nm

Electron blocking layer comprised of AlGaN with molar fraction ofaluminum of between 15% and 22% and thickness from 10 nm to 15 nm anddoped with Mg

p-GaN cladding layer with a thickness from 400 nm to 1000 nm with Mgdoping level of 5E17 cm-3 to 1E19 cm-3

p++-GaN contact layer with a thickness from 20 nm to 40 nm with Mgdoping level of 1E20 cm-3 to 1E21 cm-3

The laser device is fabricated on a nonpolar oriented surface region.Preferably, the 474 nm configured laser device uses a nonpolar (10-10)substrate with a miscut or off cut of −0.3 to 0.3 degrees towards (0001)and −0.3 to 0.3 degrees towards (11-20). The n-GaN/p-GaN is grown usingan N₂ subflow and N₂ carrier gas.

Embodiment B

In this embodiment, the invention provides a laser device capable ofemitting 486 nm wavelength light, among others, in a ridge laserembodiment. The device is provided with the following elements, as alsoreferenced in FIGS. 8 through 9.

n-GaN cladding layer with a thickness from 100 nm to 3000 nm with Sidoping level of 5E17 to 3E18 cm-3

n-side SCH layer comprised of InGaN with molar fraction of indium ofbetween 3% and 5% and thickness from 40 to 60 nm.

Multiple quantum well active region layers comprised of seven 4.5-5.5 nmInGaN quantum wells separated by eight 4.5-5.5 nm GaN barriers

p-side guide layer comprised of GaN with a thickness from 40 nm to 50nm.

Electron blocking layer comprised of AlGaN with molar fraction ofaluminum of between 15% and 22% and thickness from 10 nm to 15 nm anddoped with Mg.

p-GaN cladding layer with a thickness from 400 nm to 1000 nm with Mgdoping level of 5E17 cm-3 to 1E19 cm-3

p++-GaN contact layer with a thickness from 20 nm to 40 nm with Mgdoping level of 1E20 cm-3 to 1E21 cm-3

The laser device is fabricated on a non-polar (10-10) oriented surfaceregion (m-plane).

In a preferred embodiment, the non-polar substrate has a miscut or offcut of −0.8 to −1.2 degrees towards (0001) and −0.3 to 0.3 degreestowards (11-20). The non-polar oriented surface region has an overlyingn-GaN/p-GaN grown with H₂/N₂ subflow and H₂ carrier gas.

Embodiment C

In this embodiment, the invention provides an alternative devicestructure capable of emitting 481 nm light, among others, in a ridgelaser embodiment. The device is provided with the following elements, asalso referenced in FIGS. 9 through 10.

n-GaN cladding layer with a thickness from 100 nm to 3000 nm with Sidoping level of 5E17 to 3E18 cm-3

n-side SCH layer comprised of InGaN with molar fraction of indium ofbetween 4% and 6% and thickness from 45 to 60 nm

Multiple quantum well active region layers comprised of five 4.5-5.5 nmInGaN quantum wells separated by four 9.5-10.5 nm InGaN barriers with anindium molar fraction of between 1.5% and 3%

p-side guide layer comprised of GaN with molar a thickness from 10 nm to20 nm.

Electron blocking layer comprised of AlGaN with molar fraction ofaluminum of between 15% and 22% and thickness from 10 nm to 15 nm anddoped with Mg.

p-GaN cladding layer with a thickness from 400 nm to 1000 nm with Mgdoping level of 5E17 cm-3 to 1E19 cm-3

p++-GaN contact layer with a thickness from 20 nm to 40 nm with Mgdoping level of 1E20 cm-3 to 1E21 cm-3

The laser device is fabricated on a non-polar oriented surface region(m-plane). In a preferred embodiment, the non-polar substrate has amiscut or off cut of −0.8 to −1.2 degrees towards (0001) and −0.3 to 0.3degrees towards (11-20). The non-polar oriented surface region has anoverlying n-GaN/p-GaN grown with H₂/N₂ subflow and H₂ carrier gas.

Embodiment D

In this embodiment, the invention provides an alternative devicestructure capable of emitting 501 nm light in a ridge laser embodiment.The device is provided with the following elements, as also referencedin FIGS. 11 through 12.

n-GaN cladding layer with a thickness from 100 nm to 3000 nm with Sidoping level of 5E17 to 3E18 cm-3

n-side SCH layer comprised of InGaN with molar fraction of indium ofbetween 3% and 7% and thickness from 40 to 60 nm

Multiple quantum well active region layers comprised of seven 3.5-4.5 nmInGaN quantum wells separated by eight 9.5-10.5 nm GaN barriers p-sideSCH layer comprised of InGaN with molar a fraction of indium of between2% and 5% and a thickness from 15 nm to 25 nm.

Electron blocking layer comprised of AlGaN with molar fraction ofaluminum of between 15% and 22% and thickness from 10 nm to 15 nm anddoped with Mg.

p-GaN cladding layer with a thickness from 400 nm to 1000 nm with Mgdoping level of 5E17 cm-3 to 1E19 cm-3

p++-GaN contact layer with a thickness from 20 nm to 40 nm with Mgdoping level of 1E20 cm-3 to 1E21 cm-3

In a specific embodiment, the laser device is fabricated on a non-polar(10-10) oriented surface region (m-plane). In a preferred embodiment,the non-polar substrate has a miscut or off cut of −0.8 to −1.2 degreestowards (0001) and −0.3 to 0.3 degrees towards (11-20). The non-polaroriented surface region has an overlying n-GaN/p-GaN grown with H₂/N₂subflow and H₂ carrier gas. The laser device configured for a 500 nmlaser uses well regions and barriers fabricated using slow growth ratesof between 0.3 and 0.6 angstroms per second, but can be others. In aspecific embodiment, the slow growth rate is believed to maintain thequality of the InGaN at longer wavelengths.

In a specific embodiment, the present structure and method may havevariations. That is, the gallium nitride substrate material ischaracterized by the nonpolar crystalline surface region ischaracterized by an m-plane or others. The gallium nitrogen substratematerial characterized by the nonpolar crystalline surface region ischaracterized by an m-plane having an offcut surface orientation. Inother examples, the non-polar crystalline surface region ischaracterized by an off cut of −0.8 to −1.2 degrees towards (0001) and−0.3 to 0.3 degrees towards (11-20). In a specific embodiment, thedevice has a p-side SCH region overlying the multiple quantum wellregion, where p-side SCH region is comprised of InGaN with 0 to 7% molarfraction of InN and ranging in thickness from 5 to 70 nm. The devicealso has an electron blocking layer region overlying the multiplequantum well active region, where the electron blocking layer iscomprised of AlGaN or AlInGaN with 5 to 30% molar fraction of AlN andranging in thickness from 5 to 30 nm. A p-type cladding layer iscomprised of p-type GaN or other suitable materials. The multiplequantum well region comprises 3-5 quantum wells. Each of the barriers iscomprised of GaN and range in thickness ranges from 2.5 nm to 4.0 nm.Each of the barriers is comprised of InGaN with an InN molar fraction of1 to 5% and each of the barriers is characterized by a thickness rangingfrom 2 nm to 4.5 nm.

In an alternative specific embodiment, the present device is configuredon the semipolar crystalline surface region oriented in a {20-21} planeor {30-31} plane. The plane is offcut within +/−5 degree towards ac-plane. In other embodiments, the semipolar crystalline surface regionis oriented in a {20-2-1} plane or {30-3-1} plane. The plane is offcutwithin +/−5 degree towards a c-plane.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. Therefore, the above description and illustrations should not betaken as limiting the scope of the present invention which is defined bythe appended claims.

What is claimed is:
 1. An optical device configured to emitelectromagnetic radiation of more than about 500 nm wavelengthcomprising: a gallium nitride substrate having a nonpolar crystallinesurface region; an n-GaN cladding layer overlying the surface region,the n-GaN cladding layer having a thickness between 100 nm and 3000 nmand a Si doping level between 1E17 to 5E19 cm-3; an n-side SCH layeroverlying the n-GaN cladding layer, the n-side SCH layer comprised ofInGaN and having a molar fraction of indium between 3% and 7%, and athickness between 20 and 150 nm; a multiple quantum well active regionoverlying the n-side SCH layer, the multiple quantum well active regioncomprising a plurality of 3.5-7.5 nm InGaN quantum wells separated by1.5-7.5 nm GaN or InGaN barriers; a p-type cladding layer overlying themultiple quantum well active region, the p-type cladding layer having athickness between 400 nm and 1000 nm with a Mg doping level between 5E17cm-3 to 5E19 cm-3; a p++-type contact layer overlying the p-typecladding layer, the p++-type contact layer having a thickness between 10nm and 50 nm with a Mg doping level between 5E19 cm-3 and 1E21 cm-3; anda p-side SCH region overlying the multiple quantum well region, wherethe p-side SCH region is comprised of InGaN with 0 to 7% molar fractionof InN and has a thickness between 5 nm and 70 nm.
 2. The device ofclaim 1, wherein the nonpolar crystalline surface region ischaracterized by an m-plane.
 3. The device of claim 2, wherein thenonpolar crystalline surface region has an offcut surface orientation.4. The device of claim 3, wherein the non-polar crystalline surfaceregion is characterized by an off cut of −0.8 to −1.2 degrees towards(0001) plane and −0.3 to 0.3 degrees towards (11-20) plane.
 5. Anoptical device configured to emit electromagnetic radiation of more thanabout 500 nm wavelength comprising: a gallium nitride substrate having anonpolar crystalline surface region; an n-GaN cladding layer overlyingthe surface region, the n-GaN cladding layer having a thickness between100 nm and 3000 nm and a Si doping level between 1E17 to 5E19 cm-3; ann-side SCH layer overlying the n-GaN cladding layer, the n-side SCHlayer comprised of InGaN and having a molar fraction of indium between3% and 7%, and a thickness between 20 and 150 nm; a multiple quantumwell active region overlying the n-side SCH layer, the multiple quantumwell active region comprising a plurality of 3.5-7.5 nm InGaN quantumwells separated by 1.5-7.5 nm GaN or InGaN barriers; a p-type claddinglayer overlying the multiple quantum well active region, the p-typecladding layer having a thickness between 400 nm and 1000 nm with a Mgdoping level between 5E17 cm-3 to 5E19 cm-3; a p++-type contact layeroverlying the p-type cladding layer, the p++-type contact layer having athickness between 10 nm and 50 nm with a Mg doping level between 5E19cm-3 and 1E21 cm-3; and an electron blocking layer region overlying themultiple quantum well active region, where the electron blocking layeris comprised of AlGaN or AlInGaN with between 5 and 30% molar fractionof AlN, and having a thickness between 5 nm and 30 nm.
 6. The device ofclaim 5, wherein the nonpolar crystalline surface region ischaracterized by an m-plane.
 7. The device of claim 6, wherein thenonpolar crystalline surface region has an offcut surface orientation.8. The device of claim 7, wherein the non-polar crystalline surfaceregion is characterized by an off cut of −0.8 to −1.2 degrees towards(0001) plane and −0.3 to 0.3 degrees towards (11-20) plane.
 9. Anoptical device configured to emit electromagnetic radiation of more thanabout 500 nm wavelength comprising: a gallium nitride substrate having anonpolar crystalline surface region; an n-GaN cladding layer overlyingthe surface region, the n-GaN cladding layer having a thickness between100 nm and 3000 nm and a Si doping level between 1E17 to 5E19 cm-3; ann-side SCH layer overlying the n-GaN cladding layer, the n-side SCHlayer comprised of InGaN and having a molar fraction of indium between3% and 7%, and a thickness between 20 and 150 nm; a multiple quantumwell active region overlying the n-side SCH layer, the multiple quantumwell active region comprising a plurality of 3.5-7.5 nm InGaN quantumwells separated by 1.5-7.5 nm GaN or InGaN barriers; a p-type claddinglayer overlying the multiple quantum well active region, the p-typecladding layer having a thickness between 400 nm and 1000 nm with a Mgdoping level between 5E17 cm-3 to 5E19 cm-3; and a p++-type contactlayer overlying the p-type cladding layer, the p++-type contact layerhaving a thickness between 10 nm and 50 nm with a Mg doping levelbetween 5E19 cm-3 and 1E21 cm-3. wherein each of the barriers iscomprised of InGaN with an InN molar fraction of 1 to 5% and each of thebarriers is characterized by a thickness between 2 nm and 4.5 nm. 10.The device of claim 9, wherein the nonpolar crystalline surface regionis characterized by an m-plane.
 11. The device of claim 10, wherein thenonpolar crystalline surface region has an offcut surface orientation.12. The device of claim 11, wherein the non-polar crystalline surfaceregion is characterized by an off cut of −0.8 to −1.2 degrees towards(0001) plane and −0.3 to 0.3 degrees towards (11-20) plane.
 13. Anoptical device comprising: a gallium nitride substrate having asemipolar crystalline surface region; an n-GaN cladding layer overlyingthe surface region, the n-GaN cladding layer having a thickness from 100nm to 3000 nm and a Si doping level of 1E17 to 5E19 cm-3; an n-side SCHlayer overlying the n-GaN cladding layer, the n-side SCH layer comprisedof InGaN and having a molar fraction of indium between 3% and 8%, and athickness between 20 and 150 nm; a multiple quantum well active regionoverlying the n-side SCH layer, the multiple quantum well active regioncomprising a plurality of 2.5-6.5 nm InGaN quantum wells separated by2.5-8.0 nm GaN or InGaN barriers; a p-type cladding layer overlying theelectron blocking layer, the p-type cladding layer having a thicknessbetween 400 nm and 1000 nm with a Mg doping level between 5E17 cm-3 and5E19 cm-3; a p++-type contact layer overlying the p-type cladding layer,the p++-type contact layer having a thickness from 10 nm to 50 nm withMg doping level of 5E19 cm-3 to 1E21 cm-3; and a p-side SCH regionoverlying the multiple quantum well region, wherein the p-side SCHregion is comprised of InGaN with 0 to 7% molar fraction of InN andranging in thickness from 5 to 70 nm.
 14. The optical device of claim13, wherein the semipolar crystalline surface region is oriented in a{20-21} plane or {30-31} plane.
 15. The optical device of claim 14,wherein the plane is offcut within +/−5 degree towards a c-plane. 16.The optical device of claim 13, wherein the semipolar crystallinesurface region is oriented in a {20-2-1} plane or {30-3-1} plane.
 17. Anoptical device comprising: a gallium nitride substrate having asemipolar crystalline surface region; an n-GaN cladding layer overlyingthe surface region, the n-GaN cladding layer having a thickness from 100nm to 3000 nm and a Si doping level of 1E17 to 5E19 cm-3; an n-side SCHlayer overlying the n-GaN cladding layer, the n-side SCH layer comprisedof InGaN and having a molar fraction of indium between 3% and 8%, and athickness between 20 and 150 nm; a multiple quantum well active regionoverlying the n-side SCH layer, the multiple quantum well active regioncomprising a plurality of 2.5-6.5 nm InGaN quantum wells separated by2.5-8.0 nm GaN or InGaN barriers; a p-type cladding layer overlying theelectron blocking layer, the p-type cladding layer having a thicknessbetween 400 nm and 1000 nm with a Mg doping level between 5E17 cm-3 and5E19 cm-3; a p++-type contact layer overlying the p-type cladding layer,the p++-type contact layer having a thickness from 10 nm to 50 nm withMg doping level of 5E19 cm-3 to 1E21 cm-3; and an electron blockingregion overlying the multiple quantum well region, wherein the electronblocking layer is comprised of AlGaN or AlInGaN with 5 to 30% molarfraction of AlN and ranging in thickness between 5 nm and 30 nm.
 18. Theoptical device of claim 17, wherein the semipolar crystalline surfaceregion is oriented in a {20-21} plane or {30-31} plane.
 19. The opticaldevice of claim 18, wherein the plane is offcut within +/−5 degreetowards a c-plane.
 20. The optical device of claim 17, wherein thesemipolar crystalline surface region is oriented in a {20-2-1} plane or{30-3-1} plane.
 21. An optical device comprising: a gallium nitridesubstrate having a semipolar crystalline surface region; an n-GaNcladding layer overlying the surface region, the n-GaN cladding layerhaving a thickness from 100 nm to 3000 nm and a Si doping level of 1E17to 5E19 cm-3; an n-side SCH layer overlying the n-GaN cladding layer,the n-side SCH layer comprised of InGaN and having a molar fraction ofindium between 3% and 8%, and a thickness between 20 and 150 nm; amultiple quantum well active region overlying the n-side SCH layer, themultiple quantum well active region comprising a plurality of 2.5-6.5 nmInGaN quantum wells separated by 2.5-8.0 nm GaN or InGaN barriers; ap-type cladding layer overlying the electron blocking layer, the p-typecladding layer having a thickness between 400 nm and 1000 nm with a Mgdoping level between 5E17 cm-3 and 5E19 cm-3; and a p++-type contactlayer overlying the p-type cladding layer, the p++-type contact layerhaving a thickness from 10 nm to 50 nm with Mg doping level of 5E19 cm-3to 1E21 cm-3; wherein each of the barriers is comprised of InGaN with anInN molar fraction of 1 to 5% and range in thickness ranges from 2 nm to4.5 nm.
 22. The optical device of claim 21, wherein the semipolarcrystalline surface region is oriented in a {20-21} plane or {30-31}plane.
 23. The optical device of claim 22, wherein the plane is offcutwithin +/−5 degree towards a c-plane.
 24. The optical device of claim21, wherein the semipolar crystalline surface region is oriented in a{20-2-1} plane or {30-3-1} plane.